Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 301730

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1230 PM CDT MON MAY 30 2016

.SHORT TERM...(Today and tonight)
Issued at 320 AM CDT Mon May 30 2016

A low confidence forecast today with regards to precipitation
chances across the forecast area with high confidence for tonight.

High pressure was centered over southern Minnesota early this
morning while a warm front curved from southern South Dakota to
eastern Missouri. Small pockets of dense fog were occurring from the
north metro through Mora, west to around Hutchinson and eastward
along highway 8 in west central Wisconsin. The current forecast has
the situation handled well.

Thunderstorms have been ongoing through the night along and north of
the warm front. Cells now stretch from the southwest corner of
Minnesota to central South Dakota. The problem of the day is how far
northeast will the activity progress. The CAMS are divided with
widely varying solutions ranging from showers spreading all the way
across eastern Minnesota and western Wisconsin during the late
morning and early afternoon hours (HRRR and HOPWRF) to only a few
showers early this morning across west central through south central
Minnesota with a few more showers developing during the afternoon
across central and southern Minnesota (ARW, NMM, NSSL).

Looking at the forecast fields, the thunderstorms ongoing this
morning are in the zone of best 925-850mb moisture advection, which
correlates to the low level jet. There is also a tight gradient
across this area of negative best LI`s. As the morning progresses,
the low level jet weakens with the moisture transport axis shifting
to along the SD/MN border. The corresponding LI gradient follows
along. There is then a subtle push of these two features into
central and eastern Minnesota during the mid to late afternoon
hours. This would make it seem like the latter WRF solutions would
be more correct. The 300-305k NAM theta surfaces do show strong
upglide and low condensation pressure deficits spreading quickly
into eastern Minnesota and western Wisconsin today which is why
there is low confidence in the precipitation forecast. It could be
that the aggressive CAMS are acting on the ACCAS that will develop.
The forecast is for low pops across west central through south
central this morning with a slow spread to the Twin Cities during
the afternoon. On a side note, the NAM differential theta-e
advection points to far southern Minnesota for a good area for
thunderstorms. This may be where the storms in southwest Minnesota
end up going later this morning.

Tonight, a vigorous closed upper low will be drooping southeast
across the Northern Plains. The low level moisture transport will
increase from Omaha to the Twin Cities during the night with the
PWAT forecast to double during the night from 0.75 inches to 1.5
inches. Two thunderstorm areas are expected. One will be with the
low level jet and moisture transport (eastern/southern MN and
western WI) while the other will be a bowing line of storms headed
eastward from the Dakotas. These storms will likely be severe during
the late afternoon and evening to our west and may pose a severe
threat for a time as they move into west central Minnesota during
the late evening hours. Categorical pops remain in the forecast.

Little change was made to the high/low temperatures for
today/tonight with upper 70s to lower 80s common today with upper
50s to lower 60s tonight.

.LONG TERM...(Tuesday through Sunday)
Issued at 320 AM CDT Mon May 30 2016

The long term concerns are the thunder/severe weather threat for
tuesday and residual shower threat into Wednesday.

Various model solutions show that the shower/thunder threat will
continue into tuesday morning before it wanes through about noon.
timing of surface boundary looks o be late afternoon over east
central MN...and will keep higher pops to the east of the this
boundary into the afternoon/tuesday night. Severe weather threat
will be conditional as to how much heating will take place with
abundant cloud cover expected east of the front. The ECMWF is
slower with the movement of the front and upper trough...which
may limit overall severe weather threat. The higher shear lags the
front and more linear/multicell mode will be expected into the
evening with hail and strong winds a conditional threat into
tuesday evening.

There is some wraparound shower threat into Wednesday as the
trough moves across the area. Instability is perhaps an
isolated thunder threat. Once again...the ECMWF is more
amplified/slower with the trough and will trend a little more to
this solution for now. The overall pop trend through wednesday
was changed little from earlier forecast.

Wednesday looks to he coolest day this the cool upper
trough moves through. Temperatures will struggle to warm to 70
degrees most areas as clouds will limit overall heating potential.

the extended models diverge some on overall evolution of the
short wave trough...but they have sped up some with the main
shower/thunder threat moving in Friday and Friday night. May see
lingering chances mainly to the eastern part of the cwa as the
upper level jet stream is forecast to buckle and turn to a cooler
regime into the weekend.


.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1225 PM CDT Mon May 30 2016

Confidence remains low for this afternoon of thunderstorm
development across western Minnesota. Although confidence is high
enough to limit thunderstorm potential in eastern Minnesota until
later this evening. There remains enough instability to hold onto
VCSH/VCTS at KAXN for this afternoon, but coverage will be
isolated at best. Elsewhere, will keep VFR conditions along with
winds become more south-southeast toward 00z. Confidence remains
high for thunderstorm activity across all of Minnesota late
tonight, and into Tuesday morning (Mainly before 12z), but timing
remains problematic. Will continue the trend of TSRA or VCTS
across western Minnesota in the evening, and after 06z in eastern
Minnesota. West central Wisconsin may not see any thunderstorm
activity until after 09z. The slower movement of the frontal
boundary will lead to additional showers or thunderstorms in
eastern Minnesota by the end of the taf period.


Confidence remains high enough to keep TSRA out of the taf until
after the main aviation push this evening. However, confidence
remains high enough that thunderstorms will affect the airport
overnight, but timing remains problematic. Redevelopment is likely
Tuesday afternoon, but again timing remains problematic. Winds
will slowly become south-southeast this afternoon and continue in
this direction until Tuesday afternoon as the front nears the


TUE Night...VFR. Possible MVFR/IFR CIGS. Southwest wind 5 to 10 knots.
WED...VFR. Isolated SHRA/TSRA. West wind 10 to 15 knots.
THR...VFR. West-Northwest wind 5 to 10 knots.


.MPX Watches/Warnings/Advisories...


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